A head for our time: A look at the latest and greatest in cylinder heads for your Mopar.
Remember? It wasn't all that many years ago. You wanted to go fast in your Mopar, so you dragged a set of the "best" big block street castings, the trusty 906s, down to the basement, and hogged the ports out to tree-trunk size. Of course, you didn't waste any time on the "meaningless" bowl area. If you were lucky, after a week of breathing iron filings, maybe the car only went a tenth slower.
Then came the 1970s. Flow benches began to appear at some better equipped shops, and aftermarket heads began to emerge, such as the Zeeker big-block pieces, aluminum Hemi heads (even dual plug) and the factory's own Stage 4 iron big-block and W-2 small-block pieces. Soon, the aftermarket began duplicating the W-2s in aluminum, and, voila! A trickle of heads became an open floodgate. B-1 and Indy heads came on-line for big blocks, and we even saw Hemi heads designed to bolt up to wedge blocks. Small block lovers weren't forgotten, as the factory's W-5 aluminum castings filled a void.
were satisfied? Never! We want new iron Hemi heads! New Max Wedge
heads! Affordable aluminum small block sportsman heads!
And...and...well, you get the picture.
Sure enough, our prayers have been answered. Whereas 20 years ago the heads on your ride were almost guaranteed to be the factory-stock castings, today your choices are seemingly limitless. In fact, in the last year alone, a whole flock of new heads designed for your Pentastar powerplant have surfaced. Therefore, we figured this would be an ideal time to pursue these new offerings for Plymouth, Dodge, and Chrysler.
Mopar Performance heads
Since "the factory" is where it all started, we figured: what better place for us to begin? And, with the elephant motor the spiritual leader of all that is Mopar, it should rightfully receive priority treatment. The factory apparently agreed, as it has re-issued an updated version of the famous Street hemi iron monsters (fig. 1). These castings, available as part number P4529828, are 100% interchangeable with '66-71 castings (right down to using the same casting number), which is certainly not a bad thing. Stock 2.25/1.74", 5/16"-stem valve, are accommodated, and the chambers are virtually identical to the oldies, at 173-175cc
These beauties are, to our mind, being produced not a second too soon, as the supply of decent used iron heads, last produced in 1971, has dwindled to a precious few, and that scarcity has called up the ol' law of supply and demand. In other word, the used iron was priced like gold.
Not content to rest on their laurels, the MP team saw fit to include enough additional material in the updated castings to allow those so inclined to modify the ports for significantly better flow numbers than the original, classic piece. Right out of the box, they outflow their predecessors, in spite of having slightly less port volume. Another worthwhile virtue is that additional material has been added to critical areas that were crack prone in the older heads (in super-high-output applications). Three cheers for MP!
The second new head from Mopar Performance isn’t truly new. Rather, it’s a re-issue of a once popular head that’s been missing in action since 1488: the Stage V (that's five for you Arabic-number fans) iron head. This is a slick piece, equally at home cruising on the streets or blasting down the quarter mile. Its claim to fame is its improved flow numbers while maintaining 100% interchangeability with all earlier cast-iron production (i.e., non=max wedge) heads. In other words, bolt on a pair and go-fast.
When the heads were last seen six years ago, there were two-versions available: a stock replacement version and a ported, big-valve bracket setup. Neither utilized hardened exhaust valve seats, making them unsuitable for no-lead fuels Today's catalog lists no fewer than four versions- something for everyone. The service replacements head, which is machined for stock 2.08/1.74” valves, happily is now produced with production-type induction hardened valve seats. It’s available as part number P4529992, and despite big flow improvements over late big-block heads, is being billed as an emissions legal part. It’s this version which will potentially have the most impact on Chrysler's drag racing effort: as of this past January, NHRA has accepted the 992 as a replacement casting for all '68-'78 bigblock S/S applications! Way to go, NHRA!
If you'd like to just open the box and bolt 'em on, you can specify P5249114. This will bring you a set of 992s, assembled with single springs and the motor home Viton seals, along with the 2.08/ 1.74" valves. In other words, it's like a complete production 906 head assembly, but with better flow and hard seats. Somebody up there must be listening to our prayers after all
Third in the MP a la carte big-block main-course section is the P4529993. Starting with the same casting as the “992” version, it’s machined for mega 2.14/1.81” valves, and, in the process, the hardened valve seat area is lost.
Last but absolutely not least on the menu is the P5249112 ported version. Specifying this number will bring you a ported, race –ready version, big valves, 077 dual springs, Perfect Circle Teflon seals, chrome-moly retainers, and hardened keepers. These race-ready beauts are quoted by MP as offering a 15% flow gain over as-cast Stage Vs-certainly nothing to sneeze at.
The last in the saga of MP heads is, in reality, also not quite new: the Stage VI aluminum big-block piece. We covered this head in intimately in the February, 1993 issue, so we won't go into macrodetail here. Suffice to say that the Stage 6 is a thoroughly modern head, penned in-house by Chrysler Engineering. The bare head, P4529335, is designed to use as many stock parts as possible, including valves, rockers, headers; etc., while attaining big numbers. The six's rely on what has to be the cylinder head trick of the decade: since it's well known that raising the intake ports gives the mix a straighter shot at the bowl, the Chrysler crew raised the intake a whole bunch. Uh, special intake manifold required, right? Wrong! Just bolt the heads on your 383/400 low-deck block, then bolt up a stock 440 ("RB") manifold. Trick! (Usage on a 440 requires that set of P5249189 spacers be utilized.)
The real news about the Stage VI is just how much horsepower can be made with them. The limiting factor would seem to be the stock port window, but looks can be deceiving. The crew at Muscle Motors in Lansing, Michigan ((517] 482-4900) has built a Daytona Super Pro car as a rolling test bed for their Stage VI development work. Using a single four barrel carb, the 2200-pound car has gone a best of 8.45 secs. at 161 MPH, without ever seeing the high side of 7,000 RPM. This takes some serious power (over 700 ponies, in fact), which, in turn, takes some equally serious airflow through the heads. While MP offers ported 6s (P5249113), these guys wanted more-much more. How much is much? Well, take a look at this chart (intake).
There is one last version of the Stage 6 head available, and it's for the hardest of hard-core racers only. P4349600 will bring you a bare unmachined (for guides) casting, allowing the daring, creative types to experiment with almost unlimited freedom.
Before we drive away from the factory, we should mention that Mopar Performance is hard at work on a successor to the W-5 aluminum A-engine race heads. An all-new design, the latest castings will be known as W-7s. Utilizing a small high-swirl chamber and Jessel-type rockers, this promises to be a big step forward for SB Mopar Racers. As this is written, Ritter and Weber are running a preproduction pair on their killer Daytona. Watch this space for a full story on these in the very near future.
Everybody would love to run W-5s on their smallblock, sure! But W-5s take unique valve gear, intakes, and, usually, headers. Read: expensive! So Brodix's Dave Rotter teamed up with the B-1 crew (Wayne County Speed Shop and Koffel's Place) and formulated a completely new A-motor head, and tagged it with the confusing name, B1-BA. Cast in weight-saving aluminum, this head was designed to fill the gap between the production castings and the all-out MP stuff. As a bonus, the B1-BA is capable of utilizing nearly any rocker arm configuration on the planet, from stock-based shafts to the trick Jesel pieces (see fig. 5), which are available in a candy-store variety of ratios. And, yes, the B1-BAs can even be fitted with the AMC/Viper late-model stud-mounted rocker setup. Plus, the heads can be used on the Mopar Performance R-block, which, in most versions produced to date, oil through the pushrods like late-model Magnum truck motors.
The B1-BA is equipped with modern high-swirl 65cc chambers, and are fitted with generous 2.08" intake valves. The deck surface is significantly beefed (triangulated is the word Dave Koffel uses) to prevent the cracks that have been known to occur in this area on megapower applications. As an additional concession to crack residence, the deck surface of the new castings is a full 3/4" thick. The intake side is now almost totally free of the pushrod bulge that has driven SB Mopar porters nuts for decades. The exhaust side hat also received a considerable amount of attention, with the ports no longer being saddled with the dogleg, and are raised 0.25" for a straighter shot.
Other features of the new B1-BAs are standard-equipment 11/32" guide diameters, and the famous SB Mopar 18-degree valve inclination.
While flow testing of heads is akin to opening Pandora's box, we nonetheless decided to tough it out and have a set of box-stock castings, which we borrowed from Dave Koffel, flowed on a local shop's SuperFlow bench. As has become the standard procedure here at Mopar Action, we asked guys at the
shop (FIowTech of Yorktown Heights, NY  962-1325) to use 10" of depression. We like the 10" numbers, as we feel that this is more like what a real race motor will use, and SuperFlow uses this depression in nearly all of their engineering examples. If you're more attuned to the big numbers produced by using 28" depression, no sweat. Just remember that the 136.3 figure (at 0.60" lift) converts to a whopping 227.6 at 28" According to the very conservative figures provided by SuperFlow, this flow is adequate to feed a 465 horsepower smallblock mill, and this, with virtually as-cast ports.
Thus, it's very important to remember that these new B1-BA heads from Brodix, like all aluminum heads, are very easy to modify the big BIG numbers. That's the beauty of aluminum. Mistake? No Problem! A quick weld and try again. Of course, with a rock-solid platform like this to work with, the porter's job becomes that much easier.
The Indy Cylinder Head Company has become famous for ...yup, you guessed it, Indy cylinder heads. The main product in the Indy line is a neat aluminum casting that, for the most part, duplicates the dimensions of the original '63'64 max wedge piece. Now, Indy wows us with a cast iron version of their design.
Billed as a Stage III max wedge replacement, the Indy nonetheless deviates from the original Chrysler design in several key areas:
- Hardened exhaust valve seats
- 11/32" bronze valve guides
- Valves 1/2" longer than stock
- Valve sizes: 2.19/1.81 "
- Angled, raised plug location
All of these features
make this casting one that should have the potential for significantly
more flow (i.e., power) than the original maxi. Yet, it utilizes stock
rockers, valve covers, manifolds ...even stock gaskets. And, of course,
the durability and low-rev torque characteristics of good ol' grey cast
iron make the Indy a seemingly ideal choice for an economical killer
street motor. In addition, one wanting to create a max wedge lookalike
could save significant time and money by opting for the Indys instead
of searching for an ancient set of gennie castings of dubious quality.